Pressure is piling on Nick Clegg to expel Lord Rennard from the Liberal Democrat party after he finally apologised to four women who accused him of sexual harassment.

The ex-chief executive of the party had previously refused to say sorry having maintained his innocence over allegations that he had behaved "inappropriately".

Now it has emerged he has issued an apology in a letter sent to Liberal Democrat HQ.

Bridget Harris, a former adviser to the Deputy Prime Minister, is one of the women who made the allegations.

She resigned from the Lib Dems over the party's failure to act.

Referring to the resignation of Lord Oakeshott from the Liberal Democrats earlier this week, she told Sky News: "If one errant Lib Dem peer has actually himself walked away from the House of Lords as a result of running a few opinion polls, I think that Chris Rennard should be expected to also leave the House of Lords - basically leave public life.

Image:Bridget Harris, left, and Alison Smith, who also received an apology

"I would like to know who does he speak for now in the House of Lords?

"Who does he speak for as a Lib Dem?"

Video:Rennard Tells Women: 'I'm Sorry'

The peer's letter of apology said: "Lord Rennard wishes to achieve closure of the contentious issues that have been in the public domain for the last fourteen months by expressing his apologies to Susan Gaszczak, Alison Goldsworthy, Bridget Harris and Alison Smith.

"Lord Rennard personally accepts the full report of Alistair Webster QC as given to him on March 7th in its entirety.

"He would therefore like to apologise sincerely for any such intrusion and assure them that this would have been inadvertent.

"He hereby expresses his regret for any harm or embarrassment caused to them or anything which made them feel uncomfortable.

"Lord Rennard wishes to make it absolutely clear that it was never his intention to cause distress or concern to them by anything that he ever said or did."

Video:Handling Of Rennard Row 'Not Ideal'

Police investigated claims that Lord Rennard sexually harassed female party activists last year, but decided not to press charges.

But an internal inquiry carried out by Alistair Webster QC found there was broadly credible evidence of "behaviour which violated the personal space and autonomy of the complainants".

Lord Rennard was suspended from the party as a result of the allegations against him, but he remains a Lord.

He is now expected to make a bid to have the Lib Dem whip restored after complying with the recommendations of the inquiry.